Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Patent
1995-10-24
1997-11-18
Gorgos, Kathryn L.
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
20415811, 20415812, 570170, C07C 1700, C07C 1720
Patent
active
056883790
DESCRIPTION:
BRIEF SUMMARY
This is a national stage application of PCT/JP93/01738 filed Nov. 30, 1993.
TECHNICAL FIELD
The present invention relates to an efficient process for preparing perfluoroalkyl bromides. Perfluoroalkyl bromides are capable of providing a contrast in X-ray radiography and MR imaging, and are compounds useful as base materials for such diagnostic chemicals. Advanced contrast media for X-ray radiography and MR imaging have been developed especially from perfluorooctyl bromide.
BACKGROUND ART
To our knowledge, heat and light effect bromination perfluoroalkyl iodides with bromine, whereas we have found that this reaction requires a high temperature of at least 300.degree. C. when to be effected thermally with a high efficiency, or takes a long period of time when light is used for the progress of the reaction since IBr formed as a by-product blocks light.
Although the thermal reaction proceeds over a wide temperature range of 40.degree. to 500.degree. C., the reaction must be conducted in the presence of a radical initiator (JP-A784033/1985) or at a high temperature of not lower than 300.degree. C. (JP-A-287551/1991) if perfluoroalkyl bromides are to be prepared efficiently. When the reaction is to be conducted at such a high temperature, however, the reactor and the piping therefor need to be made of a material which is resistant to pressure and to corrosion with bromine.
On the other hand, a report was made to the effect that a perfluoroalkyl bromide was available when a perfluoroalkyl iodide and bromine were irradiated, as enclosed in a glass tube, with ultraviolet rays for 7 days is on an experimental scale, requires a long period of time and therefore appears industrially infeasible. Thus, preparation of perfluoroalkyl bromides from perfluoroalkyl iodides and bromine necessitates a long period of time in the case of the photoreaction, or a radical initiator or high temperature in the case of the thermal reaction.
An object of the present invention is to provide a process for industrially advantageously preparing a perfluoroalkyl bromide under a mild heating condition efficiently within a short period of time and in a high yield without using a radical initiator or like additive.
DISCLOSURE OF THE INVENTION
The present invention provides a process for preparing a perfluoroalkyl bromide characterized by reacting a perfluoroalkyl iodide represented by the formula (n:6.about.10) with bromine in a light-transmitting reactor with exposure to light and heating at 120.degree. to 180.degree. C. while simultaneously removing IBr resulting as a by-product by separation of a layer.
The perfluoroalkyl iodide represented by the above formula and to be used as the starting material in the present invention may be a straight-chain or branched compound. Examples of such iodides are CF.sub.3 (CF.sub.2).sub.5 I, (CF.sub.3).sub.2 CF(CF.sub.2).sub.4 I, CF.sub.3 (CF.sub.2).sub.5 I, CF.sub.3 (CF.sub.2).sub.7 I and the like. In the above formula, n is more preferably in the range of 6 to 8. Preferably, the ratio between the reactants is, for example, about 1 to about 3 moles of bromine per mole of the perfluoroalkyl iodide.
Although the reaction is conducted by placing the starting material, i.e., perfluoroalkyl iodide, into a light-transmitting reactor and adding bromine dropwise to the iodide with heating and exposure to light, a small amount of bromine may be added to the material before the reaction. The reaction can be carried out also in a continuous mode. FIG. 2 is a flow chart showing the continuous mode. Usable as the light-transmitting reactor is, for example, a flask or tube made of glass or other reactor made of glass. The reaction temperature is preferably 120.degree. to 180.degree. C. at which the perfluoroalkyl iodide generally refluxes, more preferably 140.degree. to 160.degree. C. If lower than the above-mentioned lower limit, the reaction temperature is lower than the boiling point of IBr at atmospheric pressure, making it impossible to remove IBr and consequently resulting in a greatly reduced reaction v
REFERENCES:
patent: 5051535 (1991-09-01), Von Werner
Furutaka Yasuhisa
Hisanaga Yorisato
Nakada Tatsuo
Shimokawa Kazuhiro
Ueda Souichi
Daikin Industries Ltd.
Gorgos Kathryn L.
Wong Edna
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